This might seem like a luxury, they have been around for a long time and also very expensive. Now however they are available to home users and small businesses for less than £100.
A UPS is an Uninterruptable Power Supply. It is used to maintain power to devices that need to run continuously. Things like servers, network attached storage (NAS), and to a lesser extent your router and some key network devices if you are backing up your server.
You can also use it to power your desktop PC, which should mean you never lose anything through a power failure.
They perform several important functions, one is power line conditioning, and the other is continuing to provide 240v AC to a device when the mains power to a property or office fails.
The way they do this is by charging a battery (or several batteries) in a box. The power from the batteries is passed to an inverter which regenerates the 240V AC at an output or several outputs.
If the incoming mains power is interrupted then the output of the device continues to run based on the available battery power. That is, until the battery is exhausted.
The more sophisticated ones can send signals to attached devices to ask them to shut down (gracefully).
I raise this for two reasons, I saw several models in Staples yesterday and thought about buying one. This morning I started work at 4:30am, built some graphics in Photoshop and then the power failed for under a second and my PC crashed. – Ironic! I am now seriously thinking of getting one.
The other reason is I did an IT audit for a Home-Start organisation. They have a Windows PC set up as a shared server. It is left running all of the time so the resource is available whenever someone joins the network.
They also have a fairly regular brief power cut that would cause the server to crash, and never restart. Sometimes when it was manually restarted problems would occur because of file fragments on the hard disk, and the fact that the device never shut down correctly. One could complain to the landlord, or the utility company, but you are generally stuck with the problem.
In this case a UPS is an ideal solution. Plug the UPS into the mains power, and plug the server into the UPS. You could also plug the router and any intermediate Ethernet Switches as well to maintain the network connectivity. Under these circumstances a brief power cut would have no effect on the server.
They come in a variety of sizes, and capacity. The capacity of the device measured in VA gives an indication of how long it can supply power for and at what level. The more capacity the higher the cost.
As you are not running a data centre, I would suggest that to overcome the more frequent glitch in the power to a premises then look for something around 500VA or higher. It is not going to provide power for a power cut lasting hours, but would continue to support power for up to 1 hour (depending on the load you are providing).
There are also a range of connectors that are used. The simplest solution that allows it to work out of the box uses 3 pin sockets that you can plug into using standard plugs. There is another type that has IEC sockets on it. In this case you might need a special cable or adapter if one is not supplied.
Where can I get one?
The following are worth checking out. These come from Amazon, but if you check out the product names, you will probably find them from multiple suppliers, and maybe they are cheaper.
At Amazon.co.uk: APC BE700G (click to follow the link). This entry has a useful video which also shows you how to use it. (Prices: 400VA £59.98, 550VA £68.39 and 700VA £75.98) I recommend given the small difference in price between these to go for the 700VA model.
Manufacturers claims are always on the optimistic side. Be aware that this technology has been around for decades in much more expensive and sophisticated boxes. All that has happened here is the technology is being made available at a lower price. I have read some comments that devices like these can (gracefully) shut down a device such as a PC in the event of a long power cut, but setting it up can be very time consuming.
I recommend thinking about one of these if you have power issues at your location as in the case study earlier. It will reduce the likelihood of problems occurring, but will not remove it entirely where, say the power cut lasts for 2 hours. If you can get it to tell the PC/ server it needs to shut down, then that is a bonus.
Very often though simplicity is the most attractive route. So just having backup power to cater for most power cuts should be good enough.